Compound steam engine



July 6 1926.

. G. MILLER COMPOUND STEAM ENGINE 2 Sheets-Sheet 1 Filed Feb. 4, 1924 July 6', 1926.

G. MILLER COMPOUND STEAM ENGINE 2 Sheets-$heei 2 Filed Feb. 4, 1924 m V/\ 5 K H w e m U 7// V/Y/ r/ //////4 7 7/ V Patented July 6, 1926.

UNITED STATES PATENT OFFICE.

GAVIN MILLER, OF AIRDRIE, SCOTLAND.

COMPOUND STEAM ENGINE.

Application filed February 4, 1924, Serial No. 690,427, and in Great Britain February 7, 1923.

This invention relates to arrangements of compound steam engines in which the valves are arranged to connect the high pressure cylinder with the low pressure cylinder during the stroke of the high pressure piston and to connect the high pressure cylinder with the condenser at the end of the stroke of the high pressure piston.

According to the invention the valves are so arranged as to connect the high pressure cylinder to the low pressure cylinder concomitantly with the cutting off of the supply of high pressure steam to the high pressure cylinder, and to disconnect the high pressure cylinder from the low pressure cylinder whenthe high pressure cylinder is brought into communication with the condenser at the end of the stroke of the high pressure piston.

The invention will now be described for convenience with reference to a two-cylinder compound engine, it being understood that in the application of the invention to triple expansion or quadruple expansion engines the valves sets are suitably multiplied; for the sake of clarity only the connections to one end of each cylinder are described.

In practice, there are disposed between the high pressure cylinder and the low pres sure cylinder two slide valves which are operated by eccentrics or the like and are so ported or set that steam is first admitted to the high pressure cylinder and then the supply is cut off at approximately half stroke of the high pressure piston whereupon the high pressure cylinder is brought into and maintained in communication with the low pressure cylinder during the remainder of the stroke of the high pressure piston, thereafter communication with the low pressure cylinder is interrupted when the low pressure piston is at half stroke, at which time the high pressure piston has reached the end of its stroke and the high pressure cylinder is brought into communication with the condenser and at the end of the stroke of the low pressure piston the low pressure cylinder is brought into communication with the condenser.

The invention is illustrated in the accompanying drawing in which Fig. 1 is a side elevation partly in section and Fig. 2 a partial view at right angles thereto of an engine embodying the invention. Fig. 3 is a detail sectional view of the valves in the positions occupied when the crank shaft has moved through 45 from Fig. 1 position. Figs. 4: to 9 show the valves in the positions occupied with the crank shaft advanced in stages of 4E5'each.

Referring tothe drawings, 1 denotes the high pressure cylinder, 2 the low pressure cylinder, 3 the high pressure piston and 4 the low pressure piston. 5 denotes the slide valve next to the high pressure cylinder 1 and 6 denotes the slide valve next to the low pressure cylinder 2. 7 denotes a high pres sure cylinder port and 8 denotes a low pressure cylinder port.

As shown, the valve 5, operable by the eccentric 5 on the crank shaft 17 through an eccentric rod 5 is provided with a steam inlet port 9 which is shown in Fig. 3 as in register with the port 7 so as to admit steam to the high pressure cylinder 1, such steam acting on the top of the piston 3 to effect the descent of the piston 3. By the time the piston 3 is at about half stroke, the valve 5 has been moved upwards to Fig. L position in which the port 7 is closed and the steam supply to the high pressure cylinder 1 is cut off. As the valve 5 continues to ascend to wards Fig. 5 position, and the valve 6 actuated by the eccentric 6 through the co.- centric rod 6 descends, the cylinder port 7 is brought into communication with a valve port 10 adapted to communicate in turn with a port 11 in the valve 6 in registry with the low pressure cylinder port 8, admittingsteam to the low pressure cylinder to act on the top of the low pressure piston 4; that is, the admission of steam to the high pressure cylinder 1 has been cut off and the steam therein permitted to expand and led to the low pressure cylinder 2. "When the valves are in Fig. 6 position, the piston 3 is at the bottom of its stroke and communication between the cylinders 1 and 2 is out OK. In the movement of the valves from Fig. 6 position to Fig. 7 position, the port 7 is brought into communication with the condenser 16 by way of the ports 12, 13 in the valves 5, 6 and a passage 14 formed in the wall of the cylinder 2 leading to the condenser 16. The space above the piston 3 is thereby exhausted. When the valves are in Fig. 8 position, the piston 3 has reached the return half stroke and the piston 4: is at the bottom of its downward stroke in which the cylinder port 8 is about to be brought into communication with the condenser 16 by way of the port 13 and the passage 14:. In

Fig. 9 position the port 8 is in communication with the passage 14 by way of the port 13.

The port 15 is for use in starting.

What I claim is In a compound steam engine, in combination, a conden ser, a high pressure cylinder communicatmg with said condenser through a suitable passage and formed with ports in its lateral wall, a low pressure cylinder in proximity and parallel to said high pressure cylinder and also formed with ports in its lateral wall nearest said high pressure cylinder, said wall of said low pressure cylinder being provided with a passage in communication with the condenser, a high pressure piston, a low pressure piston, two slide valves interposed between said cylinders and formed with ports adapted to register with one another and with the ports of the adjacent cylinders, said slide valves being in contact with each other and one of each working in contact with a ported lateral wall of one of said cylinders, one port of the valve nearest the low pressure cylinder being adapted to register with said passage, and means for operating said valves, said means comprising two eccentrics and connecting rods to said valves; whereby steam is first admitted to the high pressure cylinder, is then cut off at approximately half stroke of the high pressure piston, then the high pressure cylinder is brought into communication, through said valves, with the low pressure cylinder for the remainder of the stroke of the high pressure piston, then communication between the cylinders is cut off, when the low pressure piston is at about half stroke, by proper movements of said valves, then, at the end of the stroke of the high pressure piston, the high pressure cylinder is brought into communication, through said valves, with the condenser, and at the end of the stroke of the low pres sure piston the low pressure cylinder is brought into communication with the condenser.

In testimony whereof I have signed my name to this specification.

GAVIN MILLER. 

